Sound resonator



W. O. ERBES SOUND RESONATOR Nov. 24, 1931.

Filed May 30, 1930 ATTORN EY Patented Nov. 24, 1931 wanna o. iamsor svenn'rnwesru'ne'ron scum)" R's-solution 7 Application filed M1113 improved construction over the sound resonator for which Letters Patent of the United States, No. 1,484,119, were'issued to me on February 19th, 1924. v

. The objects of this invention, generally stated, are, to provide a sound resonator having an amplifier constructed mainl of a reenforced plastic composition vwhi'e fis nonresonant in charactendesigned to convey vibrations not only through the sound conduit and main sound outlet provided but also through the solid portions thereof, thereby permitting said portions to act as-a sound filtering medium to afford, in connection with said amplifier, a plurality ofsound chambers each of a diiferent amplitude and including a' sounding board and abridge, "said bridge being adapted to transmit vibrations from theamplifier to the sound chamber and sounding board and being also adjustable as to tensionso as to provide, in cooperation with the particular sound chamber with which it is connected, instrumentalities tuned to and adapted to make more resonant and harmonious tones of a certain register; and,

to make available a vent for the amplifier,

which, in connection with the sound-filterin properties impartedtothe amplifier by sai composition, relieves the amplifier of extraneous sounds caused by electrically operated speaking devices, or otherwise, and permits the sound chambers and the amplifier itself to more properly performtheir primary. functions. v I

Other objects, capabilities and advantages will appear as the descriptionof the invention progresses.

In the accompanying drawings- F igurel is a side elevation of the entire device, the same being partly in section and broken away, and having a loudspeaker installed thereon.

*Fig. 2 is a cross section drawn onth'e line 2'-2, ofFig. 1.

, Fig. 3 is a horizontal section'drawn on the line 33, of Fig.1. I i

1930. Serial 1101x570;

Hg. 4 is'a transverse sectional detail of one of a series ofsound chambers connected with the am lifier of the device, including a sounding ard bridge mounted in said Chamber. I 5

F ig. 5 is a side elevation of a modified form of said device. i i

Referring to the drawings more in detail,

a base I is provided, having at one side a pair of spaced upstanding supports 2' and at the '60 other side a pair of spaced upstanding and longer supports 3, said partsbeing, in the present embodiment of theinvention, of metallic tubular construction. A crosspiece of V Wood, denoted as 4, 'is mounted on; each pair "as of said supports, and is held against lateral displacement bys'ockets 5 made in the crosspieces adjacent their ends and adaptedto receive thefree ends of the supports. The crosspieces, designed'as the are to carry an i amplifier of substantial weight, will be further secured in place obviously by the weight 'of-said amplificrn I The amplifier includes ahollow flared body portion 10, substantially rectangular in cross 15 section, having at its front end the main outlet 11 for sounds to be conveyed therethrough and at its rear end an upstanding sound conduit 12, which communicates with the body portion. Said conduit isprovided with an 6 open and free end 13 which obviously serves as an inlet for sounds to be carried by'the amplifier, and said end also affords a seat 14 for a loudspeaker, or thelike. 15 denotes a i. sound vent located in the top of the body portion and adjacent to said conduit, and 16 a wa-ll'disposed between said vent and'conduit to prevent sounds as they are introduced into the conduit frombeing projected into the vent. I d The portions of the amplifier just described are constructed of reenforced plastic composition having nonresonant characteristics. In constructing said portions, aform is provided which is outlined to simulate said do portions,- the sections of said form utilized I in making said conduit, vent and wall, being detaehably connected with the sec- ,tion o'fflthe form used in. making the body portion, to facilitate the removal of with three spaced sockets and the rear block with a pair of spaced sockets, each denoted as 23, and 24 a pair of hardwood ribs each located at a side edge of said section, said blocks and ribs being stapled to the meshing. Said portions are now in condition to receive the scratch coat of said composition.

The plastic composition out of which I prefer to make the scratch coatof said portions of the amplifier consists of a mixture of fine sand, crushed and rolled natural rock, asbestos fiber, wood flour, magnesite, and magnesium chloride, diluted.

In preparing the composition, I use the ingredients in about the following proportions,.viz., fifty-five pounds of fine sand, fifteen pounds of said rock, fifteen pounds of asbestos fiber, fifteen pounds of wood flour, forty-five pounds of magnesite and six gallons of a 22 degree Baum solution of the megnesium chloride, the said ingredients being thoroughly blended.

The composition when thus prepared is applied with a trowel and a thickness as desired and which will serve to hold the parts in place when said coat has been dried sufficiently to permit handling, the same requiring from twelve to twenty-four hours under usual drying conditions. Said coat having been dried the form is removed, and the amplifier as now constructed is in condition to receive the frames of three sound chambers which are formed integral with said body portion. lVhile said frames vary in size one from the other, each is otherwise identical in construction and performs a like function, consequently each is given the same numerical designation, 25.

In forming one of said frames, a strip of said wire meshing of suitable width and length is cut, and a narrow section of one edge is bent in right angular relation with the body ofthe strip so as to form a flange by which the strip may be secured conveniently in an upright position to the body portion of the amplifier. Said strip having been bent into a form having a frusto-conical outline and of a size appropriate for the sound chamber of which it is a part, suitable holes are then punched through the scratch coat of the amplifier so as to expose the meshing and the strip is placed in proper position and wired to said meshing. A mold is then placed over said strip, and it is now ready to receive the plastic composition of which the frame is mainly formed.

The plastic composition out of which I prefer to make said frames and to provide a finish coat for said portions of the amplifier consists of a mixture of fine said, crushed and rolled natural rock, asbestos fiber, wood flour, magnesite, and magnesium chloride, diluted.

In preparingthe composition, I use the ingredients in about the following proportions, viz., twenty-five pounds of fine sand, twentyfive pounds of said rock, twenty-five pounds of asbestos fiber, twenty-five pounds of wood flour, forty-five pounds of magnesite and six gallons of a 22 degree Baum solution of the megnesium chloride, the said ingredients being thoroughly blended.

This composition is then placed in the mold to form said frame, strips of wood 26 being inserted in the mold and embedded in the composition in spaced relation with the outer edges of the frame, so as to afford means by which a top member may be fastened to the frame, as will be presently and more particularly described. Each of said three frames is applied to the amplifier in a like manner. When said frames have become sufficiently dried to permit handling, the molds are removed and the amplifier is in condition to receive the finish coat.

Said finish coat is applied with a trowel interiorly and exteriorly of said portions, and is smoothed down in a way to give said portions and the connections of said frames with the body portion a neat and finished appearance. As is evident, the thickness of the combined scratch and finish coats will vary with the size of the amplifier, but I have found in actual practice with this composition a maximum thickness of from three-fourths inch to one and one-fourth inches will provide structures which are substantial and satisfactory. Under ordinary drying conditions about fourteen days are reqiured for said structure to become thoroughly air cured, when it may be then painted or otherwise decorated to suit.

The amplifier, having been seated on the crosspieces 4 with the ribs 24 contacting therewith, as indicated in Fig. 1, is now in position to receive an assembly of parts disposed between it and the base. Said assembly comprises a sound chamber which is designated 30 as an entirety, the same being frusto-conical in outline and having its bottom, side and end portions constructed of maple and gen erally designated as 81, the top of said cham- .ber, which functions as a sounding board 32, being preferably of vertically grained spruce secured in place by wooden dowels. 33 denotes a reenforcing strip of maple secured to the inner periphery of the top and extending longitudinally and centrally sensitive to and designed particularly toact upon. For instance, thechamber 30 and said parts are the largestin size and two bridges .the greatest volume; The other three chambers, each of which requiresless amplitude to perform its part in the device, together with certain of their parts as ClGIiCIlbGCl, are progressively decreased in size to adapt each to the volume of sound that it is sensitive to and likewise designed to act upon. As said sound vibrations are P10]eCtQd through the ampliher, the same, ranging from the bass to the tenor as here designated, are taken up by the respective sound chamber assemblies and the tones thus actedupon are increased in resonance, are rounded out and rendered more harmonious.

The body portion of the amplifier, by virtue of its stonelike qualities and density, will permit sound vibrations to pass through it -with greater velocity than would be permitted by said sound chambers, consequentiy imperfections in the reproduction of sounds mechanically and other extraneous sounds for which said chambers are not particularly sensitive will be filtered through the body of the amplifier. It will thus be seen that the device is. equipped with resonance instrumentalities acting upon the sounds which it is desired to amplify and with a filtering medium .for eliminating undesirable sounds. The vent 15 performs useful functions in the transmission of sound vibrations through the device in that it serves to reduce air pressure in the amplifier and permits an unrestricted circulation of air therethrough; and, it also reduces the velocity of vibration so that the sounds may be amplified more slowly and evenly throughout the spaces in which the same are being acted upon.

In the embodiment of the invention shown and described, the sound chambers, includ ing the soundingboard and bridges associated therewith, are designed to be of a register similar to the violin, viola, Violoncello and bass-Viol respectively, of the usual proportions, however, certain of said chambers and said parts may be varied so as to register with the violin, viola and Violoncello of smaller sizes.

While the device shown in Fig. 1 is completely operative as a unit and may be made many suitable size, it is obvious that greater sound-volume may be had by assembling a plurality of said units, and each of which may be varied in size, as desired. Such an assembly is particularly effective where the device is utilized in large theaters, or the like, in amplifying sounds from phonographic records, radio, or in other ways.

The modified form of the invention shown in Fig. 5, is constructed in identically the same manner as described relativeto the pre ferred form of the invention, except that the sound chambers 50, 51 and 52 and the tensioning elements associated therewith are.

adapted to register with tones of the quality,

that the instrument is particularly designed to act upon, said chamber performing its functions in the manner heretofore described. The amplifier, in addition to its ordinary function, will alsoserve as a filtering medium and said vent will cooperate with the amplifier and said chamber in transmitting sounds through the device, as has been de tailed. This form may also be utilized in series, in which event each unit preferably would be adapted to act on tones of a certain register and consequently would'be of a different size, the entire assemblyserving, like the first-named assembly, to enrich and make more sonorous the sounds transmitted thereby, and also to enhance the volumeof sound.

I have found in actual practice that excellent results may also be obtained through an assembly consisting of the device as shown in Fig. 1, and three units of the modified form designed to be of a register similar to the violin, viola and Violoncello respectively.

Changes in and modifications of the construction described, other than those referred to herein, may be made without departing from the spirit of my invention or sacrificing its advantages, hence it is desired that I be not confined to the specific structures set forth, except as limited by the appended claims. Y

I claim:

1. A sound resonator, comprising a base, an amplifier supported in elevated position above the base, a sound chamber disposed between the lower periphery of the amplifier and the base, said chamber defining in its upper portion an apertured sounding board, a bridge located within said chamber and adapted to communicate sound vibrations from the amplifier to the sounding board, adjustable means for imparting tension to said bridge, said chamber, sounding board and bridge being of a certain amplitude, and a plurality of sound chambers connected with the body of the amplifier, each defining in its upper portion an apertured sounding board and having a bridge located interiorly of the chamber adapted to communicate sound vibrations from the amplifier to the sounding tension to the last-named bridges, each of the last-named chambers, including their sounding boards and bridges, being of an amplitude different from the first-named chamber, sounding board and bridge and of an amplitude difierent one from the other.

2. A sound resonator, comprising a base, an

amplifier supported in elevated position above the base, said amplifier having a hollow flared body portion constructed of nonresonant reenforced plastic material and provided with a sound inlet and a sound outlet, a vent for the amplifier, a sound chamber disposed between the lower periphery of the amplifier and said base, said chamber defining in its upper portion an apertured sounding board, a bridge enclosed within said chamber and operatively secured to the sounding board, a second bridge located exteriorly of said chamber and above the sounding board, a plurality of sound posts extending through the sounding board and connecting said bridges, a plurality of sound posts connecting the second bridge with the amplifier, and means for raising orlowering said chamber to impart tension to said bridges.

3. A sound resonator, comprising an amlifying horn made of nonresonant reenorced plastic material, a plurality of sound chambers each operatively connected with the horn and having an upper portion defining a sounding board, a bridge adapted to communicate sound vibrations from the horn to the sounding board, and means for adjustably imparting tension to the bridge,

each of said sound chambers being of a different amplitude.

' 4. In a sound resonator, an amplifier, and a plurality of sound chambers each having a sounding board and a sounding board bridge, said bridge being adapted to communicate sound vibrations from the amplifier to the sounding board, each of said sound chambers and the sounding board and bridge directly associated therewith being particularly adapted to register with tones of a different quality.

5. In a sound resonator having an amplifier, a sound chamber assembly, compris ing a sound chamber defining in its upper portion a sounding board apertured to receive sound posts and to provide sound openings, an apertured bridge located within said chamber and operatively secured to the inner periphery of the sounding board, a sec ond bridge of like construction disposed exteriorly of said chamber and above the firstnamed bridge, a plurality of sound posts extending through the sounding board and connecting said bridges, a plurality of sound posts connecting the second-named bridge with the amplifier and adapted to communicate sound vibrations from the amplifier to said bridges, and means whereby tension may be adgustably imparted to said bridges.

6. n a sound resonator having an amplifier, sound chamber operatively connected with the amplifier and defining in its upper portion an apertured sounding board, an apertured sounding board bridge located within said chamber and secured to the inner periphery of the sounding board, and adjustable means for imparting tension to said bridge.

7. In a sound resonator having an amplifier and a sound chamber associated with the amplifier, a sounding board operatively connected with said chamber, a bridge secured to said sounding board and adapted to transmit sound vibrations from the amplifier to the sounding board, and means for applying tension to said bridge.

8, In a device of the class described, an amplifying horn constructed of a nonresonant reenforced plastic composition, said horn having a hollow flared body portion provided at one end with a sound outlet and at the other end with a sound conduit communicating with said portion and having a sound inlet, a seat at the free end of said conduit for a mechanical sound reproducer, and a sound vent located adjacent said seat.

9. In a sound resonator, the combination of an amplifying horn constructed of nonresonant reenforced plastic material adapted to filter out extraneous sounds, and a plurality'of sound chambers associated with said horn each being sensitive to and active upon tones of a different register.

10. In a device of the class described, an amplifying horn having a body portion constructed of nonresonant artificial stone cementitious in character and of a density adapting it to act as a sound-filtering medium, and metallic reenforcing elements embedded in said material.

WILLIAM O. ERBES. 

